Preservac DuoVac Chamber Vacuum Sealer 350wPreservac DuoVac Chamber Vacuum Sealer 350w The Preservac DuoVac chamber vacuum sealer 350w sets itself apart by being able to vacuum seal inside the chamber and also outside the chamber just like an external bag vacuum sealer. The advantage now is that you can also do big 2 3 kg roasts that would normally be too big for the chamber, you can now use up to a 30cm wide embossed bag and have it as long and as high as you like. So for internal chamber use